Get a cheep float valv4 used for small outdoor coi ponds (around $15 or so) . Mount it to youre sump and run an airline hose from youre bucket (placed above youre sump) to the float valve. The valve is adjustable to make setting the level in the sump easy. I used a square piece of pvc that I cut off a fitting, I drilled it for the airline hose, and it works great. I dont, however, have and snails etc. in my sump to jam the float valve! BTW, my tank goes through 35 gal. of top off water / wk. and never had any probs. in the 14mos. its been set up.